<template>
  <div class="spec-preview" @mousemove="mouseMove">
    <img v-show="imgUrl" :src="imgUrl" />
    <div class="event"></div>
    <div class="big">
      <img :src="imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props: ["skuDefaultImg"],
    data() {
      return {
        imgUrl: "",
      };
    },
    watch: {
      // 初始化页面的时候skuDefaultImg是undefined 请求到数据之后的newVal 给imgurl
      skuDefaultImg(newVal) {
        this.imgUrl = newVal;
      },
    },
    mounted() {
      this.$bus.$on("getDetailImgUrl", (imgUrl) => {
        // console.log(imgUrl);
        this.imgUrl = imgUrl;
      });
    },
    methods: {
      mouseMove(e) {
        const oMask = this.$refs.mask;
        const oBigImg = this.$refs.bigImg;

        //获取鼠标到容器边缘的距离
        const mouseToBox = {
          x: e.offsetX,
          y: e.offsetY,
        };

        //获取mask元素的一半的宽高
        const oMaskWH = {
          x: oMask.offsetWidth / 2,
          y: oMask.offsetHeight / 2,
        };

        // 获取鼠标移动的距离
        const maskMove = {
          x: mouseToBox.x - oMaskWH.x,
          y: mouseToBox.y - oMaskWH.y,
        };

        // 判断临界值
        if (maskMove.x < 0) {
          maskMove.x = 0;
        } else if (maskMove.x > e.target.clientWidth - oMask.offsetWidth) {
          maskMove.x = e.target.clientWidth - oMask.offsetWidth;
        }

        if (maskMove.y < 0) {
          maskMove.y = 0;
        } else if (maskMove.y > e.target.clientHeight - oMask.offsetHeight) {
          maskMove.y = e.target.clientHeight - oMask.offsetHeight;
        }

        // 赋值
        oMask.style.left = maskMove.x + "px";
        oMask.style.top = maskMove.y + "px";

        // 控制大图移动
        oBigImg.style.left = -maskMove.x * 2 + "px";
        oBigImg.style.top = -maskMove.y * 2 + "px";
      },
    },
  };
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover ~ .mask,
    .event:hover ~ .big {
      display: block;
    }
  }
</style>
